Man-machine-environments have been developed from past host computers to current personal computers for half a century. Human life cannot exist without the computer world due to the rapid advancing of computers which provide high-speed calculation and large storage capability together with large networks. The man-machine interface (MMI) of past computers or handheld electronic devices mostly adopt keyboards and/or mice to serve as an input device, but the MMI of current computers or handheld electronic devices are changed by using a touch panel to serve as the input device. Obviously, in order to control the computer or the handheld electronic device, the physical input device such as the keyboard, the mouse, or the touch panel is required to be equipped in the computer or the handheld electronic device. Regardless of using either the keyboard, the mouse, or the touch panel that serve as the physical input device, when a user operates the computer or the handheld electronic device, anyone can see the operation contents corresponding to the computer or the handheld electronic device from the user. In other words, the input between the user and the computer or the handheld electronic device does not have privacy.